The present invention relates to a metallic tube assembly having corrosion-resistant joints. Particularly, this invention relates to metallic tube assemblies having all inside surfaces and joints comprising corrosion-resistant material. More particularly, the present invention relates to carbon or low-alloy steel oil well tubing having a corrosion-resistant liner and corrosion-resistant coupling device to provide a tube assembly wherein all inside surfaces are of corrosion-resistant material.
The perception that oil and gas reserves are dwindling has stimulated oil and gas well drillers to drill wells of greater depths, often in excess of 20,000 feet. Many of such deeper wells may contain from moderate to very high amounts of corrosives including hydrogen sulfide, carbon dioxide, fluorides, chlorides and mixtures thereof. Such wells containing corrosives, and commonly called sour wells, present severe and aggressive conditions for conventional gas and oil well tubing. Typically, such tubing is exposed to such corrosives at temperatures as high as about 300.degree. F. to 500.degree. F. or higher, which substantially increases the metals' susceptibility to corrosion. Another adverse condition to which such metallic tubing is exposed is hydrogen-induced embrittlement of the metal. Generally, such metallic tubing is made of higher strength materials which are more susceptible to hydrogen embrittlement than the lower strength metals.
Generally, carbon steel tubing is used in drilling oil and gas wells. With the requirements for deeper wells, alternative materials have been proposed in order to withstand the severe corrosive environments and conditions. A prior approach of providing inhibitors in carbon steel poses logistic problems, requires auxiliary handling and treatment facilities, is expensive and may not be economical for certain severe corrosive conditions experienced in many sour wells. Another alternative would be to completely convert from carbon steel tubing to various types of stainless steel tubing depending upon the severity of the conditions. Such an approach would be expensive because of the tonnage of stainless steel tubing required for deep wells.
Another approach would be to line the conventional metal tubing with corrosion-resistant materials. Various types of liners for tubing are known in the prior art as disclosed in U.S. Pat. Nos. 1,306,690; 1,827,437; 1,840,305; 2,258,563; 2,303,778; 3,077,661; 3,192,612; and 3,758,361. Also, the use of gaskets at pipe joints to inhibit corrosion is shown in U.S. Pat. Nos. 1,989,614; 2,201,862; 2,919,936; and 3,020,068. The practice of plating selective areas of parts to be connected is disclosed in U.S. Pat. No. 2,240,021. Additionally, various arrangements to inhibit corrosion in connected pipes are shown in U.S. Pat. Nos. 2,216,033; 3,843,170; and 4,026,583.
U.S. Pat. No. 4,366,971, issued Jan. 4, 1983, by the common Assignee of the present invention, discloses a novel tube assembly which provides that all of the inside surfaces of the assembly are resistant to corrosive attack and minimizes the cost of providing an acceptable corrosion-resistant tubing assembly. The patent disclosure pertains to providing a weld overlay or metallurgically-bonded portion of corrosion-resistant material on the ends of the tubes at the joints.
U.S. Pat. No. 3,336,054 discloses a well pipe carrying a corrosion-resistant metal liner and threaded joints for interconnecting well pipe by threaded pin and box members. The tubing may include a groove for receiving a seal member between a sleeve and an adjacent tube. U.S. Pat. No. 3,307,860 relates to a joint for well pipe having a tubular coupling and a pressure actuated seal of a deformable ring between the coupling and tubing.
There is a potential for a differential longitudinal expansion between the tube liner and the corrosion-susceptible tube of prior tube assemblies. Such expansion may be the result of a different coefficient of expansion for liner and the tube. It is most likely that the liner, made of an austenitic stainless steel, for example, would have a higher coefficient of expansion than a corrosion-susceptible tube made of carbon steel for example. A differential in longitudinal expansion may also result from exposing the liner to higher average temperatures than tube. Differential longitudinal expansion may also result from a combination of these effects and may be pronounced in deep hole wells where bottom hole temperatures may reach 400.degree. F. (204.degree. C.) or more.
There is still a need for a relatively low-cost corrosion-resistant tube assembly which facilitates easier field use and assembly by avoiding metallurgical or adhesive bonding of tubing joints and yet permits relative movement due to expansion between the liner and tubing. The assembly should include typical carbon steel or low-alloy steel tubes having a corrosion-resistant lining, yet provide expansible joint assemblies with all inside surfaces being of corrosion-resistant materials. Such tubing should also be compatible with carbon steel casing into which the tubes are inserted during service to avoid galvanic corrosion problems.